Coextrusion feedblocks are used for bringing together molten streams of thermoplastic materials from multiple extruders. The individual streams from different extruders are brought together in the coextrusion feedblock to form particular layer arrangements. The resulting multi-layer extrudate flow is then delivered to a subsequent extrusion die, or another downstream tool, to produce the desired composite coextrusion structure.
In the process of bringing together multiple streams of different plastic materials, the different materials commonly have different properties. For example, different plastics tend to exhibit different viscosities. The variations in viscosity or other properties can adversely impact the layer uniformity of the resulting multi-layer coextrusion structure. To compensate for this, it may be desirable to adjust the profile of one or more of the conduits through which the different streams pass. In the past, this has been attempted by using a variety of profiling components.
Existing profiling components have not been ideal for all applications. For example, some profiling components require off-line tuning, meaning extrusion must be stopped and the component removed and profiled by machining and polishing. Further, certain adjustable profiling components are rigidly attached to control shafts, and the rigid attachment can cause flow instability. Still further, some known profiling systems offer less adjustability, and hence less control over profiling, than would be ideal for certain applications.
It would be desirable to provide coextrusion feedblocks and coextrusion profiling insert assemblies that address these and other problems associated with adjustable coextrusion feedblocks.